Box folding machine



Now-.28, 19330 1w. LOW 1,931,027

BOX FOLDING MACHINE Filed Nov. 23, 1931 16 Sheets-Sheet l II 'I 1 v m h r 7* I W 'Y' v 42 ITIOR 42 I95 I JOHN WILLIAM LOW I I96 azs r ATTORNEY.

FIG. 11.

Nov. 28, 1933.

J. W. LOW

BOX FOLDING MACHINE Filed Nov. 23. 1931 16 Sheets-Sheet 2 IINVENTOR OHN WILLAM LOW BY I 9 ATTORNEY.

Nov. 28, 1933.'

J. W. LQW

Box FOLDING MACHINE Filed Nov. 25. 1931 16 sheuysheet 3 I22 "Ll m -4 v r \r fizs was.

I INVENTOR: JOHN wu.

LIAM LOW z W ATTORNEY.

Nov. 28, 1933. J. w. LOW 1,937,027

BOX FOLDING MACHINE File d Nov. 25. 1931 16 SheetsSheet 4 JOHN WILLIAM LOW ATTORNEY J. w. LOW 1,937,027.

ox FOLDING MACHINE Nov. 28, 1933.

Filed Nov. 23. 1951 le'sheets-sheet 5 FIG. 5. v

'4" v mvsmog; JOHN WILLIAM LOW 5Y3 I I ATTORNEY Nov. 28, 1933. 4 J. w. LOW 1,937,027

!3OX FOLDING MACHINE Filed Nov. 25. 1931 1s Sheets-Sheet 6 IF I16. 6.

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JOHN WILLIAM LOW g 7 ATTORNEY.

J. W; LOW

BOX FOLDING MACH fNE Nov. 28, 1933.

Filed NOV 25. 1931 16 Sheets-Sheet 8 IFIIG. 8.

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BOX FOLDING MACHINE I Filgd Nov. 23. 1931 16 Sheets-Sheet 9 V D Y INVENTOR JOHN WILLIAM LOW ATTORNEY.

Nov. 28, 1 933. J w ow BOX FOLDING MACHINE Filed Nov. '23, 1931 16 Sheets-Sheet 10 m. no.

I NVENTOR JOH N WILLIAM LOW ATTORNEY.

Nov. 28, 1933.

IF "6. Illl.

43 lf;\ I 7 Q IN'VENTOR:

JOHN WILLIAM LOW 236 WW 1 w ATTORNEY.

Nov 1933' .1. w. LOW "1337,02? v BOX FOLDING MACHINE" Filed Nov. 23. 1931 IGSheets-Sheetli? FllG., l2.

7 g 'INVENTOR: JOHN. WILLIAM-LOW AT TORNEY Nov. 28, 1933.

J. w. LOW BOX FOLDING MACHINE Filed No 25/1931 16 Sheets-Sheet 13 He. n25.

IN V ENT:OTR JOHN WILLIAM LOW ATTORNEY.

No 28, 1933. I J. w. LOW 1,937,027

BOX FOLDING MACHINE File d NOV. 23; 1931 16 Sheets-Sheet l4 ZIZ . JOHN WILLIAM LOW ,"79

ATTORNEY INVENTOR:

Nov. 28, I933. J. w. LOW 1,937,027

BOX FOLDING MAdHINE Filed No v. 23. 1931 l6 Sheets-Sheet 15 I 'IIIIIIlIIIIIII/IIIIIIIIIIIIIIIIIIIIIIIIIII IIIIIIIIIIIIIIIIIIIIJ YIIIII/IIIIl/IIIIIIII/IIIIIIIIIlIIII/llfllfi r11 \\\\\.\\Y

III (III/II n w INVENTOR Iol JOHN WILLIAM L ATTORNEY Nov."28, 1933. w

BOX F OLDING MACHINE Filed Nv. 25. 1931 15 Sheets-Sheet 1e O 2 m F INVENTOR: JOHN WILLIA MLO 13mg ATTORNEY Patented No.1 28, 1933 PATENT- OFFICE 1,937,027 I BOX rommc mom John William Low, Mill Valley, Callf., assignor, by mesne assignments, of one-half to Edgar L.

Stern and one-half to Raoul J. Gruenberg, both of San Francisco, Calif.

' Application November 23,1931 Serial No. 576,643

12 Claims.

This invention relates to improvements in box folding machines and'more particularly to a machine for folding boxes of the class shown in the patent to Edgar L. Stern, Number 1,463,448, dated July 31, 1923, entitled Folding box.

Among the objects of the invention is to provide a machine that will automatically feed and fold box blanks seriatim and interlock the tabs and slots to form fully assembled collapsed boxes 0 ready for immediate use when opened.

. blank set up in position therein Another object'is to reduce the cost of product and improve the quality of folding boxes.

' Another object is to increase the speed of production of such boxes.

Another object-is to design the machine to insure against scarring and crumpling the boxes during production: I

A further object is to produce a machine requiring but the minimum of attention of the operators.

In the accompanying drawings and the following description the invention is disclosed in its preferred form. It is to be understood, however, that it is not limited to this form because it may be embodied in other forms within the purview of the claims following the description.

In the sixteen sheets of drawings: Fig. 1 is a plan view of a paper box folding v machine constructed in accordance with this invention.

Fig. 2 is a side elevation of the same showing the driving mechanism for the several operating shafts.

Fig. 3 is a fragmentary plan view partly in horizontal section taken below the line IIIIII, Fig. 2 showing the box folding mechanism with a box prior to the folding operation.

Fig- 4 is a similar view showing thepositions of the folding mechanism while the folding operation is in progress. Fig. 5 is a transverse vertical section of the folding mechanism taken on the line V, Fig. 1, and showingthe plates for folding the sides of the box blank and the blades for inserting the tongues of the blank into the sides.

Fig. .6 is a similar view taken on the line VI, Fig. 1, and showing an extension of Fig. 5 to be read in conjunction therewith.

Fig. 'lis a longitudinal vertical section taken on the line VII, Fig. 1, and showing the plates for folding the ends of the box blank and the bell cranks for bending the tabs of the box into po- Fig. 8 is a similar view taken on the line VIII and showing an extension of Fig. 7 to be read in conjunction therewith. Fig. 9 is a transverse vertical section taken onthe line 1X,'Fig. 1, and showing the mechanism 0 for folding one of the sides of the box lid.

Fig. 10 is a similar view taken on the line x, Fig. 1, and showing an extension of Fig. 9 to be read in conjunction therewith.

Fig. 11 is a longitudinal vertical section taken on the line XI-XI, Fig. 1, and showing the pivot ed plunger for folding the box lid. 1

Fig. 12 is a fragmentary rear elevation view showing the cam driven levers for operating the lid folding plunger.

Fig. 13 is a transverse vertical section taken on the line XIIIX1II, Fig. 1, and showing the mechanism for timing the feeding of the box blanks into the folding mechanism. I

Fig. 14 is a fragmentary vertical section of 15 the plunger for placing the box blank in the folding mechanism.

Fig. 15 is a fragmentary rear elevation of the cam and rack for driving the plunger shown in Fig. 14.

Fig. 16 is an enlarged horizontal section-of one of the plates for folding the ends of the box and showing the mounting of the bell cranks which fold the tabs of the box.

Fig. 17 is a fragmentary detail in horizontal section showing one of the tab folding bell cranks in tripped position. 4 r

. Fig. 18 is a'fragmentary detail view in side elevation showing the means for operating one of the wipers which coact with the descending box 00 blank plunger.

Fig. 19 is a fragmentary vertical section of the driving means for the rollers for ejecting the folded boxes.

Fig.- 20 is a plan view of a box blank adapted to be folded by the present machine. v

Fig. 21 is a plan view from above of a'box folded by the present machine.

Fig. 22 is a vertical section of one. of the corners of the box during the folding operation.

The present machine is designed to fold the type of folding box illustrated in Figs. 20, 21 and 22. It is obvious, however, that the machine may be modified by those skilled in the artto fold other forms and sizes of folding boxes. b 106 The blank shown in Fig. 20 is formed of fold able box board and is longitudinally scored at ab and transversely scored at cdel. These score. lines divide the blank respectively into the lid and bottom g-h, the ends 5-1, and 110 i the locking flap k, in longitudinal alinement. The body of the box has the sides Z-m extending transversely therefrom on opposite sides, while the lid g has the transverse slides 11-0. The locking tabs p-q-r-s extend transversely from the ends i-i and are cut away at t-u. to form the obliquely extending tongues 12.

The sides Z-m are pierced to form the obliquely disposed biarcuate slots w-x-y-z which the sides l-m and the bottom 71.. This forces the tongues 1: completely through the slots w to z to lock the ends i-i and the sides l-m together.

The sides n-o of the box lid are folded over on the lines a-b to. overlie the body of the lid. The. lid y then follows the end i as it is folded over on the score line e and assumes the position shown in Fig. 21, overlying the body of the box.

In detail, the construction of the machine illustrated in the drawings, referring more particularly to Figs. 1 and 2 comprises: The main frame having the pillars 1-1, 2-2, 3-3, and 4-4 on each side of the machine. These pillars are fixed together by the horizontal side rails 5-6-7-8 to form a rigid structure. Additional reinforcing bars such as 9-10-11 are fixed to the pillars 1 to 4 to increase the rigidity and stability of the frame.

The large pulley 12 is mounted on the shaft 13 which is supported between the out bearing 14 and the pillar 3. The pulley is engaged by the belt 15 and driven from any suitable prime mover such as an electric motor. l

The shaft 16 extends between the pillars 3-3 and is driven at about 35 R. P. M. by the pulley 12 through the reduction gearing 17-18. The cam shaft 19 is mounted in the journal brackets- 20-21 which are fixed on the side rail 7. This shaft is driven by the shaft 16 through the sprockets 22-23 and the chain 24 at the same speed ratio.

The longitudinal cam shaft 25 is mounted in the journals 26-27 at right angles to the shaft 19 and is driven thereby through the miter gears 28-29 mounted on the shafts 19 and 25 respectively. The miter gear 30 is mounted on the opposite end of the shaft 25 and meshes with the gear 31 to drive the shaft 32 upon which it is mounted. This cam shaft 32 extends parallel with the shaft 19 and is mounted in the brackets 33-34 fixed to the side rail 6. The three cam shafts 19, 25, 32 are thus driven by the shaft 16 at the same ratio of speed, 35 R. P. M.

The tops of the pillars. 1-1, 2-2, and 4-4 are joined by the transverse angle supports 35-36-37- upon which are mounted the longitudinal pair of rails 38-38. The conveyor belts 39-39 overlie the rails 40 and each encircles a set of pulleys 41-42-43-44 mounted on the shafts 45-46-47-48, respectively.

The 'sprocket'49 is mounted on one end of the shaft. 46 and engages within the chain 50. The sprocket 51 is mounted on thepower driven shaft 32 and drives the chain 50 and sprocket 49. Thus the pulleys 42-42 are rotated, moving the 69!}- .roller 61.

veyor belts 39-39 in the direction of the arrows in Fi l.

The inclined table 52 ismounted at the side of the pillars 1-1 and terminates adjacent the ends of the rails 33. The pile of blanks X is placed on the table 52and are fed manually seriatim onto the conveyor belts 39-39.

The angle guides 53-53 extend alongside the belts 39 throughoutthe length of the rails 38 to maintain the blanks in perfect alinement on' the belts 39.

The-rollers 54-54 are fixed on the shaft 55 which is rotatably mounted in suitable brackets on the angles 53 adjacent the end of the table 52. The lower circumference of the rollers impinge on the belts 39. Thus, a box blank placed on the conveyor belts 39 is pressed vdown upon the belts by the rollers 54 to insure against possible slipping due to the inertia of the blank.

The two vertical stops 56-56 (see Fig. 13) are located between the rails 38-38 and their upper ends project slightly above the plane of the blank X lying on the conveyor belts 39. Thus the blanks are halted in their travel on the conveyor belts 39 upon contacting the stops 56 (see Figs. 1 and 13). The blanks are then fed in timed relation into the folding mechanism as follows:

The lower ends of the stops 56-56 are fixed to the cross bar 5'7 which has the depending block 58 resting on the end of the cam follower lever 59 (see Figs. '7 and 13) The lever 59 is pivoted on the bracket 60 and has the roller 61 riding on the "kidney cam 62. This cam is mounted on the power driven shaft 19 and maintains the lever 59 and the stops 56in raised position except when r the depression 63 on the cam comes under the The stops 56 then fall of their own weight and permit the blank X to continue its travel on the conveyors 39.

The uprights 64-64 are fixed at each end of 1-15 the cross bar 57 and are slidable in the guides 65-65 which are fixed to the frame of the machine. Thus, the guides 65direct the movement of both the stop 56 and the cross bar 57 and the other members of this feeding mechanism. The

laterally extending brackets 66-66 are fixed to the upper ends of the uprights 64 and mount the ends of the shaft 67,

The pair of rollers 68-68 are rotatably mounted on the shaft 67 above the conveyor belts 39. I

When the stops 56 are depressed bythe operation of the cam 62, the rollers 68 are also lowered to contact the blank X. The blank is thus pressed down upon the moving. belts 39 to insure its being carried away into position over the folding mechanism. When the blank reaches its proper position over the folding mechanism,

its front edge contacts against the angle stop 69 to prevent further movement (see Fig. 1). r The pillars 3-3 of the frame of the machine .135 have the upward extensions '70-'70 which are cross connected at their upper ends by the channel beam 71. The guide bracket '12 is bolted to the center of the channel and slidablymounts the rack '73. Theplunger '74 is mounted at the 1%. lower end of the rack '73 and is adapted to be lowered to press the blank X" into position between, giie fglding members of the machine, as shown in 8.... The gear 75 (see Fig. 15 is mounted on the' shaft '76v in the bracket 72 and-meshes with the rack '73 to govern the movements of the plunger.

The opposite end of the shaft '76 is mounted in the bracket. 7'7 and has the pinion 7'7- fixed thereed in the bracket 77' and the guide '19 and has the rack teeth 80 enmeshed with the pinion 77.

The cam 81 is mounted on the power driven shaft 16 and has the irregular contour 82 X" downward into the folding mechanism, the

ends i-iand the sides Z-m of the box blank are wiped up against the sides of the plunger.

perpendicular to the bottom h.

The wiper plates 86-87 (see Figs. 1, 7, 8, 13 and 18) are pivoted transversely across the rails 38 onthe brackets 88-88 depending from'the rails on opposite sides of the plunger 74. The wiper plates normally rest in a horizontal plane supported by the lugs 89-89 extending transversely from the brackets 88.

The wiper 86 is adapted to be raised into vertical position by the'plate 90 which is pivoted at 91 to the bracket 88 (see Figs. 7, 13 and 18). The arm 92 projects vertically from the plate 90 and impinges on the cam surface 93 provided at the end of the wiper 86. The spring 94 contracts between the cam 93 and the arm 92 to resiliently maintain the arm in engagement with the cam surface.

The lug 95 depends from the opposite side of the pivoted plate 90 and is connected to the link 96. The cam follower lever 97 is fulcrumed on the bracket 98 and is pivoted at its upper end to the link 96; The operating cam 99 is fixed on the rotating shaft 19 and engages the roller provided at the lower end of the lever 97.

When the raised portion of the contour of the, cam 99 strikes the roller 100, the link 96 is drawn rearward and swings the plate 90 on its pivot. The arm 92 is thus raised and causes the wiper 86 to assume a vertical position, thus folding the end 7' of the box blank upward between the wiper and the descending plunger 74.

The wiper 871s operated similarly to the wiper 86 by the pivoted plate 90'. The link 96' connects the plate 90 to the lever 97 pivoted at 98'. The cam 99' is mounted on the power driven shaft 32 and engages the roller 100' to oscillate the lever 97'. The cams 99 and 99' are timed together to operate the wiper plates 86-87'synchronously as the plunger 74 descends. The wiper 87 folds the end i of the box blank upward on the line e to assume a. vertical position perpendicular to the bottom It in a plane parallel with the opposite end 7'.

The blocks 101-101 (see Figs. 1, 5, 7 and 13) are fixed opposite each other on therails 38 between the conveyor belts 39-39. The faces of the blocks 101 are cut away at each end to form inclined bevel surfaces as at 102. The thin plates 103-103 are mounted on the faces of the blocks 101 and extend laterally to overlie the inclined surfaces 102.

When the plunger 74 descends, the sides Z-m of the box blankimpinge on the plates 103 and are folded up vertically between the plates and the plunger, as the plunger continues its descent.

. This is accomplished immediately after the ends i-a' are folded by the wiper pla es 86-87.

' The tabs p-q-r-s impinge upon the edge of the conveyor belt and are forced upward and inward toward each other thereby. The conincrease the rigidity of the Figs. 3, 4, 5 and 7).

lever 142 is pivoted at 143 3 tinuation of the movement of the plunger carries the tabs p to s downward between the inclined surfaces 102 of the blocks 101 and the plates 103 and bends the tabs into a vertical plane parallel with the'sides l-m. 80

When the plunger passes below the plane of the blocks 101, the blank assumes the position shown in Fig. 3 in the folding mechanism with the tabs p-q-r-s lying on the outside of the sides l-m.

The bed plate 104 is rigidly mounted on the sills 105-105 (see Figs. 2, 5, 7 and 8) which extend between the pillars 2-4 and 2-4 on opposite sides of the machine. The transverse reinforcing angles 106-106 extend between the sills 105-105 under the edges of the bed plate to,

structure. 1 The sides l-m of the box blank are folded in-' ward and downward on the score lines a-b to overlie the bottom h by the plates 107-108 (see These plates are pivoted on the brackets 109 fixed to the bed plate 104 and cut away as at 110 to clear the tabs. p-q- 111 which is fixed on the rotating shaft 25. The lever .113, fulcrumed on the bracket 114, is provided at its lower end with the cam roller 115 and is connected to the cross link 116 at 117. The spring 118 contracts between the lug 119 on 105 the cross link 116 and the frame of the machine and resiliently maintains the roller 115 impinging on the contour of the cam 111. The lever 120 on the opposite side of the machine is pivoted at 121 and is connected at its lower end to 110 the end of the cross link 1117. The links 122- 122' join the upper ends of the levers 113, 117 to the lugs 123 fixed adjacent the upper edges of the plates 107-108.

When the roller 115 is displaced by the cam 115 111, the upper ends of the levers 113. 120- are swungtogether by the cross link 116. The links 122-122- thus tilt the plates 107-108 downward, folding thesides l-m of the blank to overlie the bottom h. 120

The plates 124-125 extend between the guides 126-126, 127-127 and are slidably mounted in the inclined grooves 128-129 therein (see Figs.

5, 6, 7 and 8). The blades 130-130, 131-131 extend from the lower ends of the inclined plates 5 124-125 opposite the slots w-m-u-z in the. blank X".

The ends of the blades 130, 131 are beveled as I at 132 (Fig. 5) to form a thin edge adapted to enter the slots w to z in the blank. The edge 130 132 is cut away to form the inclined portions 133-134 at each side and leaving the central projecting portion 135.

The upwardly extending cam plates 136-136 are fixed at theintersection of the blades 130- 131 and the plates 124-125. The cam plates, have the inclined curved surface 137 which extends tangentially to the blades 130, 131 to cooperate with the tabs p-q-r-s of the blank as hereinaf er set forth.

The plates 124-125 are operated by the cam 138 which is mounted-on the power driven shaft 25. The lever 139 is pivoted on the bracket 140 1 and has the roller- 141 mounted at its lower end to impinge on the contour of the cam 138.- The on the opposite side of the machine.

The link 144 is pivoted at 145 tothe lever 139' and is connected to the lower end of the lever 142 F to cause the two levers to operate in unison. The

spring 146 contracts between the depending lug 147 on the link 144 and the frame of the machine to urge the roller 141 into engagement with the earn 139. The short links 148-148 connect the upper ends of the levers 139-142 to the lugs 149 fixed to the underside of the inclined plates 124-125.

When the rotation of the cam 138 displaces the roller 141, the upper ends of the levers 139-142 are swung together by the link 144. This slides the plates 124-125 in the inclined grooves 128-129 and carries the blades 130-130, 131-131 forward and downward to pass on each side of the cut away portions 110 of the pivoted plates 107-108. This is accomplished during the folding of the sides Z-m of the box blank by the operative movement of the plates 107-108.

The projecting portions 135 of the edges of the blades 130-130, 131-131 enter the biarcuate slots w-zc-y-z while the sides Z-m are yet in an inclined position before the end of the movement of the folding plates 107-108. The continuation of the movement of the blades projects the inclined portions 133-134 into the slots of the box blank to open up the entire length of the slots.

The inclination of the grooves 128-129 causes the blades 130, 131 to descend obliquely to bring the edges 132 into proximity with the top surface of the bed plate 104. The blades thus press downward in the slots w-x-y-z to hold the sides Z-m fiat on the bottom h after the restoration of the folding plates 107-108 to vertical position. The ends of the blades 130-131 are longitudinally curved at (see Figs. 3 and 7) to part the edges of the slots 20 to 2 into different planes to facilitate the insertion of the tabs p-q-r-s as hereinafter described.

The ends i-a' of the box blank are folded down on top of the ends of the folded sides Z-m by the plates 151-152 (see Figs. 3, 4, 7, 8, 16 and 17). These folding plates are pivoted on" each side adjacent their lower edge on the small brackets 153.

The folding plates 151-152 are operated by the cams 154-154 fixed on the rotating shafts 19 and 32 respectively. The levers 155-155 are mounted opposite each other on the brackets 156-156 and are provided with the rollers 157-157' at their lower ends. The springs 158-158 contract between the upper ends of the levers and the frame of the machine to urge the rollers 157-157 into contact with the contours of the operating cams.

The upper ends of the over to form the horizontal arms 159-159 projecting toward each other. The ends of the arms 159-159 are provided with the pins 160-160 projecting through the vertically grooved lugs 161-161 on the rear sides of the folding plates 151-152. The strips 162 of thin metal are riveted to the ends of the arms 159 and impinge on the ends of the pins 160 to prevent the pins from slipping out of the grooved lugs 161.

Displacement ofthe rollers 157-157 by the cams 154-154 swings the arms 159 toward each other. This tilts the plates 151-152 forward and downward to fold over the ends i-7' of the box on the lines 6- The pin and slot connection 160-161 between the levers 155 and the folding plates, compensates for the incidental downward thrust incurred by the arcuate movements of the levers and pivoted plates.

The bell cranks 163-163 are pivoted at each' end of the folding plates 151-152 as is best shown in Figs. 3, 4 and 13. The ends 164 of the bell are tapered and have curved 'oif edges resilient brackets 181-181 levers 155-155 are bent .168-168 toward each which project in front of the planes of the folding plates (see Fig. 16) and engage the tabs .p-qr-s of the blank adjacent the score lines a and b.

The plates.151-l52 have the longitudinal internal grooves 166. which are covered by the face plates 167. The slides 168-168 are mounted in the grooves 166 and project therefrom at each end. The projecting ends of the slides are bent laterally at 169 to form pivoting brackets for the bell cranks 163. The inner ends of the slides are bent rearward to form the lugs 170 projecting through the slots 171 in the rear surface of the plates 151-152.

The pins 172-172 areset in the slides 168 and project through "the slots 173 provided in the rear of the folding plates. The springs 174-174 contract between the projecting pins 172 and the pins 174'-174' fixed to the plates 151-152. slides 168 are thus urged outwardly by the springs 174 to project the ends 169 to the fullest. extent.

The levers 175-175 are pivoted at 176 adjacent the ends of the lugs 177-177 which extend laterally from the operating arms 159-159'. The ends of the levers 175 terminate alongside the lugs 170 and are adapted to engage the lugs to operate the slides 168. The opposite ends of the levers 175 are bent inward toward each other at 178to form the angularly disposed ends 179-179 extending toward the arms 159.

The stationary cams 180-180' depend from the which are fixed to the frame of the machine. The guide channels 182 integral with the cams 180 straddle'the arms 159 to maintain the cams in lateral alinement.

The faces of the cams are beveled as at 183 to form inclined cam surfaces in the plane of the angularly offset lever ends 179 (see more particularly Figs. 7 and 16) The grooves 184 are cut in the cam faces 183 and are adapted to be engaged by the pins 185 fixed in the lever ends 179.

When the arms 159-159' are operated to tilt the plates 151-152 to fold the ends 5-9 of the box blank, the levers 175 are also moved longitudinally.

This brings-the angularly disposed ends 179 into engagement with the cam surfaces 183. The pins 185 engage the grooves 184, thus preventing the cams'l80 from rising out of contact with the lever ends 179.

The continuation of the longitudinal movement of the levers 175 draws the lever ends 179 along the inclined cam surfaces 183, thus tilting the levers 175 on their pivots 176. The opposite ends of the levers then engage the lugs 170 and draw the slides other, as in Fig. 4. This presses the ends 164 of the tabs p-q-r-s of inwardly on the score lines 11-21. v

As the folding of the ends i-j progresses, the tabs p to s are pressed against the curved faces 137 of the cam-plates 136. This resiliently curls the tabs 12 to s and enters the lower edges '0 of the tongues 11 between the parted edges of the slots the bell cranks 163 against the blank and bends them 7 the lines W-b The of which are bent again at 187 to lie against the rear surface of the end folding plates 151-152. When the slides 168 are withdrawn into the grooves 166 to the fullest exten by the operation 

